This invention relates to the drilling of a well in the earth, and more particularly to measuring torque and hook load in a process for detecting problems in the drilling operation.
The problems encountered in drilling through the earth to very deep depths have been well documented and successfully solved. These problems are exacerbated in directional drilling where the path of the drill bit deliberately deviates substantially from the vertical direction. The insertion of tubulars, drill strings, casings, and tubing into very high angle boreholes is particularly difficult.
More specifically, the drilling problems which occur in directional drilling include keyseating which occurs in severely deviated wells when the diameter of the hole at the point of curvature is not sufficient to allow free movement of the drill string. If the situation is not corrected by boring out the well at the critical point, the drill string will become stuck. Differential pressure sticking is a problem caused by the pressure of the drilling mud pushing the drill string against one wall of the well so as to block off drilling mud from an area of the drill string at which a low pressure is developed. This problem, if not identified and corrected promptly, will cause sticking. Ploughing is a borehole problem resulting from the tool joints and/or stabilizers cutting into soft formations or settled cuttings as the drill string moves axially. The accumulation of cuttings at one location in the well will eventually disrupt the drilling operation. Drilling muds with low lubricity will increase the drag and torque during the drilling operation, and in some cases make the drilling operation impossible.
It is an object of the present invention to provide an improved method of measuring the pick up, running in, and free rotating loads on the drill string for use in a computer aided method of determining drilling problems such as that described above.
It is another object of the present invention to plot hook loads as a function of time as a way of identifying drilling problems.